Gallery, Projects and General > How do I??
Electric heater for hot air engine?
vtsteam:
Well, off on an experiment using the previously tested stainless steel aircraft safety wire, and a plaster of Paris housing.
To begin with, I found a piece of 1" PVC water pipe which had an OD of close to 1-1/2" (38mm) and cut off about a 3 inch (76 mm) length. I wrapped it with the safety wire and taped the coils in place. Then I crimped a couple wires onto the ends using some copper tubing and a wire crimper. The wires were high temp type salvaged from a dead oil filled electric radiator.
vtsteam:
Then I cut a small cardboard box down to the rough dimensions I wanted, taped it back together and lined it with kitchen plastic wrap as a mold for the plaster.
I painted Vaseline on the coil form as a release agent.
vtsteam:
I poked a hole through the top of the water pipe with a hot length of piano wire, heated over the kitchen stove. I used that to suspend the heating coil over the mold. I had to coil the wires up to one side to get the coil to stand vertically. The through wire was located from one end of the mold, at the center height of No. 83's displacer cylinder.
Oh, forgot to mention earlier, the bottom of the water pipe was covered with tape, so the plaster couldn't rise up inside.
A piece of masking tape was used to tie the sides of the mold box together to prevent bulging at the top.
vtsteam:
Plaster of Paris was combined with water, the lumps squeezed out by hand, and then I added about one third by volume of fine sand. this was mixed again, and I poured the mold.
I found that even with the weight of the heater and wires, it still wanted to float up sideways, pivoting on the wire. So I spooned sand into the pipe, which provided enough weight to keep it vertical.
Now to wait......
vtsteam:
I let the plaster cure overnight before unmolding it.
I figured that removing the core pipe might give me some problems because of the tape and I had thought of several clever ways to get it out of there. But giving it a simple twist with pliers back and forth a tiny amount, and pulling slowly freed it quite easily.
The coil of wire stayed in place. All in all a satisfying little job. Will it work to run the engine? No idea!
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